1. Field of the Invention
The present invention relates to a device for reducing the power demand for the propulsion of a single-propeller or multi-propeller ship, in particular for broad-built or non-broad-built ships that are not very fast.
2. Description of the Related Art
From DE 42 23 570 C1 discloses a flow guide surface for a controllable-pitch propeller is known. This flow guide surface includes a ring-shaped nozzle that is arranged upstream to influence the flow in the manner of a diffuser. To this effect deceleration of the flow in the near region, and acceleration of the flow in the outer region is carried out. The diffusor diameter is smaller than 65% of the propeller diameter. Such a nozzle is designed as a deceleration nozzle or diffuser with an outwardly curved ring-shaped nozzle. This diffusor decelerates the flow in its region, which can only result in an improvement of propulsion efficiency if very thick hubs are used, such as in the case of controllable-pitch propellers. Such a nozzle is thus not designed as an acceleration nozzle with an inwards curvature of the ring-shaped nozzle. The nozzle presented in the above-mentioned printed publication thus does not accelerate the flow in its region, and is not suitable for all propeller types, in particular it is not suitable for fixed propellers. DE 42 23 570 C1 does not describe an effective principle of a fore-nozzle, which principle consists of increasing the propeller flow speed in regions where the main stream is very high.
JP 07 267189 A discloses a propeller arrangement with a ring-shaped nozzle and fins that are arranged in a star-shape. The propeller diameter approximately corresponds to the ring diameter of the nozzle.
JP 58 000492 A shows a further propeller arrangement which is said to result in an improvement in the efficiency and a reduction in the power demand for propulsion. This arrangement also comprises fins, as well as a structure comprising six elements arranged in a honeycomb-like manner.